Northwest Territories, region of northern and northwestern Canada, encompassing a vast area of forests and tundra. Throughout most of the 20th century the territories constituted more than one-third of the area of Canada, and they reached almost from the eastern to the western extremities of the country, across the roof of the North American continent. The creation in 1999 of the territory of Nunavut out of the eastern portion of the Northwest Territories reduced the area of the latter by more than half.